The present invention is based on a fuel injector according to the species defined in the main claim.
World Patent WO 93/18299 already describes a fuel injector having a valve seat body on which a guide element rests which possesses a central passage opening through which a valve needle can move axially. This inner passage opening in the guide element is manufactured very accurately with small tolerances since the axially movable valve needle is guided in it. Outside of this central passage opening, a plurality of passage openings is produced in the guide element to permit passage of flow which have a circular form themselves and which are uniformly arranged in the guide element in a circular shape. Therefore, the fuel flow route lies outside of the central passage opening.
At the upstream face of the guide element, a thin filter element is formed as an additional component. In this context, in a center, ring-shaped filter zone, countless circular filter openings are provided. The filter element completely covers the guide element with its passage holes.
Equally, it is already known from documents German Patent 39 16 459 A1 and U.S. Pat. No. 5,642,862 to provide a guide disk near the valve seat on injection valves, the guide disk having a central guide opening and flow openings lying outside of this guide opening.
The fuel injector according to the present invention having the characterizing features of the main claim has the advantage of achieving a functional integration in a simple manner which is attained by a simplified manufacturability and a reduced number of manufacturing processes in a particularly inexpensive manner. According to the present invention, the functional integration is achieved in that in a component designed as a guide disk for axially guiding a valve needle only one opening is provided which is used both as guide opening and as flow opening.
Advantageous embodiments and improvements of the fuel injector characterized in the main claim are made possible by the measures specified in the subclaims.
The inner passage opening in the guide disk is advantageously made by punching. Thus, in doing so, an opening which both guides the valve needle and realizes the passage of the fuel is made in one process step. Further openings are not needed in the guide disk so that no additional manufacturing processes are required.
Since the guide disk takes a fixed position relative to the valve seat, a well-directed flow against the orifice plate is made possible which is not variable over the service life. When using the new guide disk, unlike valve needles having flow grindings on the circumference, no spray angle tolerances or flow tolerances occur which can disadvantageously arise in the case of the known valve needles because of the possible rotation and the changing relative position with respect to the spray openings during operation.